带有 TikZ 的树：分支上的标签的位置和一些特殊性

Question

我在进行测试时将标签“p”和“1 - p”放在分支上：有没有更严格的方法？

我需要复制图像中的树，但我不确定如何完成。

 \documentclass{article} 
 \usepackage{tikz}
 \usepackage{amsmath}
 \usetikzlibrary{trees}
 \begin{document}
 \begin{tikzpicture}

 \node {}[grow'=right,blue!80,
         level 1/.style={sibling distance=50mm,level distance=25mm},
         level 2/.style={sibling distance=25mm,level distance=25mm},
         level 3/.style={sibling distance=15mm,level distance=25mm}]
 child {node {S}
   child {node {S}
     child {node {S} edge from parent node[above,pos=0.5] {$p$}}
     child {node {$\overline{\text{S}}$}
     edge from parent node[below=4pt,pos=0.5] {$1-p$}}
     edge from parent node[above=4pt,pos=0.5] {$p$}}
   child {node {$\overline{\text{S}}$}
     child {node {S} edge from parent node[above,pos=0.5] {$p$}}
     child {node {$\overline{\text{S}}$}
     edge from parent node[below=4pt,pos=0.5] {$1-p$}}
     edge from parent node[below=6pt,pos=0.5] {$1-p$}}
     edge from parent node[above=8pt,pos=0.5] {$p$}}
 child {node {$\overline{\text{S}}$}
    child {node {S}
      child {node {S} edge from parent node[above,pos=0.5] {$p$}}
      child {node {$\overline{\text{S}}$}
       edge from parent node[below=6pt,pos=0.5] {$1-p$}}
       edge from parent node[above,pos=0.5] {$p$}}
      child {node {$\overline{\text{S}}$}
      child {node {S}
       edge from parent node[above,pos=0.5] {$p$}}
     child {node {$\overline{\text{S}}$}
       edge from parent node[below=6pt,pos=0.5] {$1-p$}}
       edge from parent node[below=6pt,pos=0.5] {$1-p$}}
       edge from parent node[below=8pt,pos=0.5] {$1-p$}};

     \node at (25mm,60mm) { Épreuve 1};
     \node at (50mm,60mm) { Épreuve 2};
     \node at (75mm,60mm) { Épreuve 3};
  \end{tikzpicture}
  \end{document}

Answer 1

我会只使用“原始”tikz 而不是树来实现这一点。这样我就能更好地控制事物。我为您提供了一种简单的方法，可能需要进行大量调整（尺寸、位置等）。调整一切的一种方法可能是声明参数，尤其是在环境中\newcommand。

\documentclass[tikz, border=2mm]{standalone}
\usepackage    {ifthen}
\usetikzlibrary{calc}

\newcommand{\branch}[2] % vertex, height
  { 
    \pgfmathsetmacro\ang{atan(#2*0.5/1.8)}; % angle of rotation (labels p and 1-p)
    \node (top) at ($#1+(2,#2*0.5)$)  {$S$};
    \node (bot) at ($#1+(2,-#2*0.5)$) {$\overline{S}$};
    \draw[thick,blue] (top) -- ($#1+(0.2,0)$) --(bot);
    \node[rotate= \ang] at ($#1!0.5!(top)$) [above] {$p$};
    \node[rotate=-\ang] at ($#1!0.5!(bot)$) [below] {$1-p$};
  }
  
\newcommand{\bdots}[2] % vertex, height
  { 
    \node (top) at ($#1+(2,#2*0.5)$)  {};
    \node (bot) at ($#1+(2,-#2*0.5)$) {};
    \draw[thick,blue,dotted] (top) -- ($#1+(0.2,0)$) --(bot);
  }

\begin{document}
\begin{tikzpicture}[line join = round, line cap = round]
  %\draw[gray] (0,0) grid (11,9);
  % 1st column
  \branch{(0,3.5)}{4};
  % 2nd column
  \branch{(2,5.5)}{2};
  \branch{(2,1.5)}{2};
  % 3rd row
  \branch{(4,6.5)}{1};      
  \branch{(4,4.5)}{1};
  \branch{(4,2.5)}{1};
  \branch{(4,0.5)}{1};
  % 4th column (dotted lines)
  \bdots {(6,5  )}{1};
  \bdots {(6,2  )}{1};
  % n-th column
  \branch{(9,7  )}{1};
  \branch{(9,4.5)}{1};
  % dots
  \foreach\y in{0.5,2,5,6.5}
  {
    \node at (8.5,\y) {$\cdots$};
  }
  \foreach\y in{3,5.5}
  {
    \node at (10,\y)  {$\cdots$};
  }
  % labels
  \foreach\x [count=\i] in{2,4,6,11}
  {
    \node at (\x,8.5) {\bf\sffamily Épreuve};
    \node at (\x,8)   {\ifthenelse{\equal{\i}{4}}{$n$}{$\i$}};
  }
\end{tikzpicture} 
\end{document}

它看起来像这样：